1. Field of the Invention
This invention relates generally to trocars having valves which seal against instruments operable through a working channel in the trocar.
2. Discussion of the Prior Art
Mechanical trocars typically included a cannula defining a working channel, and a housing which encloses valves that function to inhibit the escape of insufflation gasses. The cannula of the trocar is adapted to be positioned across the abdominal wall of a patient using an obturator which is initially inserted into the working channel and then removed once the cannula is in place. Various elongate instruments can be inserted through the working channel of the trocar to reach, and perform operative functions, at a site within the abdomen. It is the function of the valves to engage the outer surface of such an instrument and form seals around the instrument to prevent the escape of insufflation gasses.
Trocar valves are commonly formed from elastomeric materials which are highly susceptible to puncture and tearing by sharp instrument configurations. Since many instruments, and of course the obturator, typically have sharp distal tips, it has become particularly desirable to protect the valves from these objects.
In some cases the valves have been operable by lever arms which have provided the valves with variable diameters. In such a configuration, protective shields have been provided for attachment to the obturators. These shields have functioned with the lever arms to expand the valve. Shields have also been designed to extend between the seal and the sharp distal tip of the obturator as disclosed and claimed in applicant's copending application Ser. No. 07/909,075, filed Jul. 2, 1992 and entitled Seal Protection Mechanisms, now abandoned, which is incorporated herein by reference. Such shields have been adapted solely for use with obturators and are not necessarily applicable to other types of instruments.
Other valve protectors have functioned relative to the lever arms in response to insertion of any instrument into the working channel. Such a mechanism is disclosed and claimed in applicant's copending application Ser. No. 07/952,300 filed on Sep. 28, 1992 and entitled Seal Protection Mechanism, which is incorporated herein by reference.
In spite of these advances in the art, it has remained desirable to provide a mechanism which can protect an ordinary septum valve devoid of any lever mechanism and also to limit friction on the instrument during axial passage through the valve. In the absence of a protection mechanism for the ordinary septum seal, instruments having sharp tips have been free to engage the valve often resulting in damage to the valve which renders the entire trocar inoperable. Even in those instances where the valve is not cut or otherwise damaged, large instruments which are required to move through a small orifice in a septum valve have experienced significant friction forces making axial movement of the instrument difficult.